lib/cpumask.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 #include <linux/slab.h>
   3 #include <linux/kernel.h>
   4 #include <linux/bitops.h>
   5 #include <linux/cpumask.h>
   6 #include <linux/export.h>
   7 #include <linux/bootmem.h>
   8
   9 /**
  10  * cpumask_next - get the next cpu in a cpumask
  11  * @n: the cpu prior to the place to search (ie. return will be > @n)
  12  * @srcp: the cpumask pointer
  13  *
  14  * Returns >= nr_cpu_ids if no further cpus set.
  15  */
  16 unsigned int cpumask_next(int n, const struct cpumask *srcp)
  17 {
  18         /* -1 is a legal arg here. */
  19         if (n != -1)
  20                 cpumask_check(n);
  21         return find_next_bit(cpumask_bits(srcp), nr_cpumask_bits, n + 1);
  22 }
  23 EXPORT_SYMBOL(cpumask_next);
  24
  25 /**
  26  * cpumask_next_and - get the next cpu in *src1p & *src2p
  27  * @n: the cpu prior to the place to search (ie. return will be > @n)
  28  * @src1p: the first cpumask pointer
  29  * @src2p: the second cpumask pointer
  30  *
  31  * Returns >= nr_cpu_ids if no further cpus set in both.
  32  */
  33 int cpumask_next_and(int n, const struct cpumask *src1p,
  34                      const struct cpumask *src2p)
  35 {
  36         while ((n = cpumask_next(n, src1p)) < nr_cpu_ids)
  37                 if (cpumask_test_cpu(n, src2p))
  38                         break;
  39         return n;
  40 }
  41 EXPORT_SYMBOL(cpumask_next_and);
  42
  43 /**
  44  * cpumask_any_but - return a "random" in a cpumask, but not this one.
  45  * @mask: the cpumask to search
  46  * @cpu: the cpu to ignore.
  47  *
  48  * Often used to find any cpu but smp_processor_id() in a mask.
  49  * Returns >= nr_cpu_ids if no cpus set.
  50  */
  51 int cpumask_any_but(const struct cpumask *mask, unsigned int cpu)
  52 {
  53         unsigned int i;
  54
  55         cpumask_check(cpu);
  56         for_each_cpu(i, mask)
  57                 if (i != cpu)
  58                         break;
  59         return i;
  60 }
  61 EXPORT_SYMBOL(cpumask_any_but);
  62
  63 /**
  64  * cpumask_next_wrap - helper to implement for_each_cpu_wrap
  65  * @n: the cpu prior to the place to search
  66  * @mask: the cpumask pointer
  67  * @start: the start point of the iteration
  68  * @wrap: assume @n crossing @start terminates the iteration
  69  *
  70  * Returns >= nr_cpu_ids on completion
  71  *
  72  * Note: the @wrap argument is required for the start condition when
  73  * we cannot assume @start is set in @mask.
  74  */
  75 int cpumask_next_wrap(int n, const struct cpumask *mask, int start, bool wrap)
  76 {
  77         int next;
  78
  79 again:
  80         next = cpumask_next(n, mask);
  81
  82         if (wrap && n < start && next >= start) {
  83                 return nr_cpumask_bits;
  84
  85         } else if (next >= nr_cpumask_bits) {
  86                 wrap = true;
  87                 n = -1;
  88                 goto again;
  89         }
  90
  91         return next;
  92 }
  93 EXPORT_SYMBOL(cpumask_next_wrap);
  94
  95 /* These are not inline because of header tangles. */
  96 #ifdef CONFIG_CPUMASK_OFFSTACK
  97 /**
  98  * alloc_cpumask_var_node - allocate a struct cpumask on a given node
  99  * @mask: pointer to cpumask_var_t where the cpumask is returned
 100  * @flags: GFP_ flags
 101  *
 102  * Only defined when CONFIG_CPUMASK_OFFSTACK=y, otherwise is
 103  * a nop returning a constant 1 (in <linux/cpumask.h>)
 104  * Returns TRUE if memory allocation succeeded, FALSE otherwise.
 105  *
 106  * In addition, mask will be NULL if this fails.  Note that gcc is
 107  * usually smart enough to know that mask can never be NULL if
 108  * CONFIG_CPUMASK_OFFSTACK=n, so does code elimination in that case
 109  * too.
 110  */
 111 bool alloc_cpumask_var_node(cpumask_var_t *mask, gfp_t flags, int node)
 112 {
 113         *mask = kmalloc_node(cpumask_size(), flags, node);
 114
 115 #ifdef CONFIG_DEBUG_PER_CPU_MAPS
 116         if (!*mask) {
 117                 printk(KERN_ERR "=> alloc_cpumask_var: failed!\n");
 118                 dump_stack();
 119         }
 120 #endif
 121
 122         return *mask != NULL;
 123 }
 124 EXPORT_SYMBOL(alloc_cpumask_var_node);
 125
 126 bool zalloc_cpumask_var_node(cpumask_var_t *mask, gfp_t flags, int node)
 127 {
 128         return alloc_cpumask_var_node(mask, flags | __GFP_ZERO, node);
 129 }
 130 EXPORT_SYMBOL(zalloc_cpumask_var_node);
 131
 132 /**
 133  * alloc_cpumask_var - allocate a struct cpumask
 134  * @mask: pointer to cpumask_var_t where the cpumask is returned
 135  * @flags: GFP_ flags
 136  *
 137  * Only defined when CONFIG_CPUMASK_OFFSTACK=y, otherwise is
 138  * a nop returning a constant 1 (in <linux/cpumask.h>).
 139  *
 140  * See alloc_cpumask_var_node.
 141  */
 142 bool alloc_cpumask_var(cpumask_var_t *mask, gfp_t flags)
 143 {
 144         return alloc_cpumask_var_node(mask, flags, NUMA_NO_NODE);
 145 }
 146 EXPORT_SYMBOL(alloc_cpumask_var);
 147
 148 bool zalloc_cpumask_var(cpumask_var_t *mask, gfp_t flags)
 149 {
 150         return alloc_cpumask_var(mask, flags | __GFP_ZERO);
 151 }
 152 EXPORT_SYMBOL(zalloc_cpumask_var);
 153
 154 /**
 155  * alloc_bootmem_cpumask_var - allocate a struct cpumask from the bootmem arena.
 156  * @mask: pointer to cpumask_var_t where the cpumask is returned
 157  *
 158  * Only defined when CONFIG_CPUMASK_OFFSTACK=y, otherwise is
 159  * a nop (in <linux/cpumask.h>).
 160  * Either returns an allocated (zero-filled) cpumask, or causes the
 161  * system to panic.
 162  */
 163 void __init alloc_bootmem_cpumask_var(cpumask_var_t *mask)
 164 {
 165         *mask = memblock_virt_alloc(cpumask_size(), 0);
 166 }
 167
 168 /**
 169  * free_cpumask_var - frees memory allocated for a struct cpumask.
 170  * @mask: cpumask to free
 171  *
 172  * This is safe on a NULL mask.
 173  */
 174 void free_cpumask_var(cpumask_var_t mask)
 175 {
 176         kfree(mask);
 177 }
 178 EXPORT_SYMBOL(free_cpumask_var);
 179
 180 /**
 181  * free_bootmem_cpumask_var - frees result of alloc_bootmem_cpumask_var
 182  * @mask: cpumask to free
 183  */
 184 void __init free_bootmem_cpumask_var(cpumask_var_t mask)
 185 {
 186         memblock_free_early(__pa(mask), cpumask_size());
 187 }
 188 #endif
 189
 190 /**
 191  * cpumask_local_spread - select the i'th cpu with local numa cpu's first
 192  * @i: index number
 193  * @node: local numa_node
 194  *
 195  * This function selects an online CPU according to a numa aware policy;
 196  * local cpus are returned first, followed by non-local ones, then it
 197  * wraps around.
 198  *
 199  * It's not very efficient, but useful for setup.
 200  */
 201 unsigned int cpumask_local_spread(unsigned int i, int node)
 202 {
 203         int cpu;
 204
 205         /* Wrap: we always want a cpu. */
 206         i %= num_online_cpus();
 207
 208         if (node == -1) {
 209                 for_each_cpu(cpu, cpu_online_mask)
 210                         if (i-- == 0)
 211                                 return cpu;
 212         } else {
 213                 /* NUMA first. */
 214                 for_each_cpu_and(cpu, cpumask_of_node(node), cpu_online_mask)
 215                         if (i-- == 0)
 216                                 return cpu;
 217
 218                 for_each_cpu(cpu, cpu_online_mask) {
 219                         /* Skip NUMA nodes, done above. */
 220                         if (cpumask_test_cpu(cpu, cpumask_of_node(node)))
 221                                 continue;
 222
 223                         if (i-- == 0)
 224                                 return cpu;
 225                 }
 226         }
 227         BUG();
 228 }
 229 EXPORT_SYMBOL(cpumask_local_spread);